From f166a8d1f52f1fda1a64d8cd50f17275d63c8843 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Mon, 9 Dec 2019 13:42:49 +0000 Subject: [PATCH 1/2] Remove SnapshotCache in favour of ResponseCache --- synapse/handlers/initial_sync.py | 19 +++--- synapse/util/caches/snapshot_cache.py | 94 --------------------------- tests/util/test_snapshot_cache.py | 63 ------------------ 3 files changed, 8 insertions(+), 168 deletions(-) delete mode 100644 synapse/util/caches/snapshot_cache.py delete mode 100644 tests/util/test_snapshot_cache.py diff --git a/synapse/handlers/initial_sync.py b/synapse/handlers/initial_sync.py index 81dce96f4b..73c110a92b 100644 --- a/synapse/handlers/initial_sync.py +++ b/synapse/handlers/initial_sync.py @@ -26,7 +26,7 @@ from synapse.streams.config import PaginationConfig from synapse.types import StreamToken, UserID from synapse.util import unwrapFirstError from synapse.util.async_helpers import concurrently_execute -from synapse.util.caches.snapshot_cache import SnapshotCache +from synapse.util.caches.response_cache import ResponseCache from synapse.visibility import filter_events_for_client from ._base import BaseHandler @@ -41,7 +41,7 @@ class InitialSyncHandler(BaseHandler): self.state = hs.get_state_handler() self.clock = hs.get_clock() self.validator = EventValidator() - self.snapshot_cache = SnapshotCache() + self.snapshot_cache = ResponseCache(hs, "initial_sync_cache") self._event_serializer = hs.get_event_client_serializer() self.storage = hs.get_storage() self.state_store = self.storage.state @@ -79,17 +79,14 @@ class InitialSyncHandler(BaseHandler): as_client_event, include_archived, ) - now_ms = self.clock.time_msec() - result = self.snapshot_cache.get(now_ms, key) - if result is not None: - return result - return self.snapshot_cache.set( - now_ms, + return self.snapshot_cache.wrap( key, - self._snapshot_all_rooms( - user_id, pagin_config, as_client_event, include_archived - ), + self._snapshot_all_rooms, + user_id, + pagin_config, + as_client_event, + include_archived, ) @defer.inlineCallbacks diff --git a/synapse/util/caches/snapshot_cache.py b/synapse/util/caches/snapshot_cache.py deleted file mode 100644 index 8318db8d2c..0000000000 --- a/synapse/util/caches/snapshot_cache.py +++ /dev/null @@ -1,94 +0,0 @@ -# -*- coding: utf-8 -*- -# Copyright 2015, 2016 OpenMarket Ltd -# -# Licensed under the Apache License, Version 2.0 (the "License"); -# you may not use this file except in compliance with the License. -# You may obtain a copy of the License at -# -# http://www.apache.org/licenses/LICENSE-2.0 -# -# Unless required by applicable law or agreed to in writing, software -# distributed under the License is distributed on an "AS IS" BASIS, -# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -# See the License for the specific language governing permissions and -# limitations under the License. - -from synapse.util.async_helpers import ObservableDeferred - - -class SnapshotCache(object): - """Cache for snapshots like the response of /initialSync. - The response of initialSync only has to be a recent snapshot of the - server state. It shouldn't matter to clients if it is a few minutes out - of date. - - This caches a deferred response. Until the deferred completes it will be - returned from the cache. This means that if the client retries the request - while the response is still being computed, that original response will be - used rather than trying to compute a new response. - - Once the deferred completes it will removed from the cache after 5 minutes. - We delay removing it from the cache because a client retrying its request - could race with us finishing computing the response. - - Rather than tracking precisely how long something has been in the cache we - keep two generations of completed responses. Every 5 minutes discard the - old generation, move the new generation to the old generation, and set the - new generation to be empty. This means that a result will be in the cache - somewhere between 5 and 10 minutes. - """ - - DURATION_MS = 5 * 60 * 1000 # Cache results for 5 minutes. - - def __init__(self): - self.pending_result_cache = {} # Request that haven't finished yet. - self.prev_result_cache = {} # The older requests that have finished. - self.next_result_cache = {} # The newer requests that have finished. - self.time_last_rotated_ms = 0 - - def rotate(self, time_now_ms): - # Rotate once if the cache duration has passed since the last rotation. - if time_now_ms - self.time_last_rotated_ms >= self.DURATION_MS: - self.prev_result_cache = self.next_result_cache - self.next_result_cache = {} - self.time_last_rotated_ms += self.DURATION_MS - - # Rotate again if the cache duration has passed twice since the last - # rotation. - if time_now_ms - self.time_last_rotated_ms >= self.DURATION_MS: - self.prev_result_cache = self.next_result_cache - self.next_result_cache = {} - self.time_last_rotated_ms = time_now_ms - - def get(self, time_now_ms, key): - self.rotate(time_now_ms) - # This cache is intended to deduplicate requests, so we expect it to be - # missed most of the time. So we just lookup the key in all of the - # dictionaries rather than trying to short circuit the lookup if the - # key is found. - result = self.prev_result_cache.get(key) - result = self.next_result_cache.get(key, result) - result = self.pending_result_cache.get(key, result) - if result is not None: - return result.observe() - else: - return None - - def set(self, time_now_ms, key, deferred): - self.rotate(time_now_ms) - - result = ObservableDeferred(deferred) - - self.pending_result_cache[key] = result - - def shuffle_along(r): - # When the deferred completes we shuffle it along to the first - # generation of the result cache. So that it will eventually - # expire from the rotation of that cache. - self.next_result_cache[key] = result - self.pending_result_cache.pop(key, None) - return r - - result.addBoth(shuffle_along) - - return result.observe() diff --git a/tests/util/test_snapshot_cache.py b/tests/util/test_snapshot_cache.py deleted file mode 100644 index 1a44f72425..0000000000 --- a/tests/util/test_snapshot_cache.py +++ /dev/null @@ -1,63 +0,0 @@ -# -*- coding: utf-8 -*- -# Copyright 2015, 2016 OpenMarket Ltd -# -# Licensed under the Apache License, Version 2.0 (the "License"); -# you may not use this file except in compliance with the License. -# You may obtain a copy of the License at -# -# http://www.apache.org/licenses/LICENSE-2.0 -# -# Unless required by applicable law or agreed to in writing, software -# distributed under the License is distributed on an "AS IS" BASIS, -# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -# See the License for the specific language governing permissions and -# limitations under the License. - - -from twisted.internet.defer import Deferred - -from synapse.util.caches.snapshot_cache import SnapshotCache - -from .. import unittest - - -class SnapshotCacheTestCase(unittest.TestCase): - def setUp(self): - self.cache = SnapshotCache() - self.cache.DURATION_MS = 1 - - def test_get_set(self): - # Check that getting a missing key returns None - self.assertEquals(self.cache.get(0, "key"), None) - - # Check that setting a key with a deferred returns - # a deferred that resolves when the initial deferred does - d = Deferred() - set_result = self.cache.set(0, "key", d) - self.assertIsNotNone(set_result) - self.assertFalse(set_result.called) - - # Check that getting the key before the deferred has resolved - # returns a deferred that resolves when the initial deferred does. - get_result_at_10 = self.cache.get(10, "key") - self.assertIsNotNone(get_result_at_10) - self.assertFalse(get_result_at_10.called) - - # Check that the returned deferreds resolve when the initial deferred - # does. - d.callback("v") - self.assertTrue(set_result.called) - self.assertTrue(get_result_at_10.called) - - # Check that getting the key after the deferred has resolved - # before the cache expires returns a resolved deferred. - get_result_at_11 = self.cache.get(11, "key") - self.assertIsNotNone(get_result_at_11) - if isinstance(get_result_at_11, Deferred): - # The cache may return the actual result rather than a deferred - self.assertTrue(get_result_at_11.called) - - # Check that getting the key after the deferred has resolved - # after the cache expires returns None - get_result_at_12 = self.cache.get(12, "key") - self.assertIsNone(get_result_at_12) From b1e7012deea2d254ecbf92d1fed429c34a65db54 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Tue, 10 Dec 2019 11:29:44 +0000 Subject: [PATCH 2/2] Newsfile --- changelog.d/6506.misc | 1 + 1 file changed, 1 insertion(+) create mode 100644 changelog.d/6506.misc diff --git a/changelog.d/6506.misc b/changelog.d/6506.misc new file mode 100644 index 0000000000..99d7a70bcf --- /dev/null +++ b/changelog.d/6506.misc @@ -0,0 +1 @@ +Remove `SnapshotCache` in favour of `ResponseCache`.